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前言

本文对雷达波形的内容以思维导图的形式呈现，有关仿真部分进行了讲解实现。

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一、雷达波形

思维导图如下图所示，如有需求请到文章末尾端自取。

二、Matlab 仿真

1、SFW 的距离分辨率和距离模糊

距离分辨率 $\Delta R=\frac{c}{2n\Delta f}$

不模糊距离窗为 $R_u=\frac{c}{2\Delta f}$

①、MATLAB 源码

hrr_profile.m

function [hl] = hrr_profile (nscat, scat_range, scat_rcs, n, deltaf, prf, v, rnote,winid)
% Range or Time domain Profile
% Range_Profile returns the Range or Time domain plot of a simulated 
% HRR SFWF returning from a predetermined number of targets with a predetermined
% RCS for each target.
c=3.0e8;  % speed of light (m/s)
num_pulses   = n;
SNR_dB = 40;
nfft = 256;
%carrier_freq = 9.5e9; %Hz (10GHz)
freq_step    = deltaf; %Hz (10MHz)
V = v;  % radial velocity (m/s)  -- (+)=towards radar (-)=away
PRI = 1. / prf; % (s)
if (nfft > 2*num_pulses)
    num_pulses = nfft/2;
else
end
Inphase = zeros((2*num_pulses),1);
Quadrature = zeros((2*num_pulses),1);
Inphase_tgt    = zeros(num_pulses,1);
Quadrature_tgt = zeros(num_pulses,1);
IQ_freq_domain = zeros((2*num_pulses),1);
Weighted_I_freq_domain = zeros((num_pulses),1);
Weighted_Q_freq_domain = zeros((num_pulses),1);
Weighted_IQ_time_domain = zeros((2*num_pulses),1);
Weighted_IQ_freq_domain = zeros((2*num_pulses),1);
abs_Weighted_IQ_time_domain = zeros((2*num_pulses),1);
dB_abs_Weighted_IQ_time_domain = zeros((2*num_pulses),1);
taur = 2. * rnote / c;
for jscat = 1:nscat
   ii = 0;
   for i = 1:num_pulses
      ii = ii+1;
      rec_freq = ((i-1)*freq_step);
      Inphase_tgt(ii) = Inphase_tgt(ii) + sqrt(scat_rcs(jscat)) * cos(-2*pi*rec_freq*...
         (2.*scat_range(jscat)/c - 2*(V/c)*((i-1)*PRI + taur/2 + 2*scat_range(jscat)/c)));
      Quadrature_tgt(ii) = Quadrature_tgt(ii) + sqrt(scat_rcs(jscat))*sin(-2*pi*rec_freq*...
         (2*scat_range(jscat)/c - 2*(V/c)*((i-1)*PRI + taur/2 + 2*scat_range(jscat)/c)));
   end
end
if(winid >= 0)
    window(1:num_pulses) = hamming(num_pulses);
else
    window(1:num_pulses) = 1;
end
Inphase = Inphase_tgt;
Quadrature = Quadrature_tgt;
Weighted_I_freq_domain(1:num_pulses) = Inphase(1:num_pulses).* window';
Weighted_Q_freq_domain(1:num_pulses) = Quadrature(1:num_pulses).* window';
Weighted_IQ_freq_domain(1:num_pulses)= Weighted_I_freq_domain + ...
   Weighted_Q_freq_domain*j;
Weighted_IQ_freq_domain(num_pulses:2*num_pulses)=0.+0.i;
Weighted_IQ_time_domain = (ifft(Weighted_IQ_freq_domain));
abs_Weighted_IQ_time_domain = (abs(Weighted_IQ_time_domain));
dB_abs_Weighted_IQ_time_domain = 20.0*log10(abs_Weighted_IQ_time_domain)+SNR_dB;
% calculate the unambiguous range window size
Ru = c /2/deltaf;
hl = dB_abs_Weighted_IQ_time_domain;

numb = 2*num_pulses;
delx_meter = Ru / numb;
xmeter = 0:delx_meter:Ru-delx_meter;
plot(xmeter, dB_abs_Weighted_IQ_time_domain,'k')
xlabel ('relative distance - meters')
ylabel ('Range profile - dB')
grid

例如，假设距离像起始点为 $R_0=912m$ 处，RCS 为 $\sigma =10m^2$，$v=15m/s$ 的运动目标的合成距离像

fig3_17.m

clear all
close all
nscat = 1;
scat_range = 912;
scat_rcs = 10;
n =64;
deltaf = 10e6;
prf = 10e3;
v = 15;
rnote = 900,
winid = 1;
count = 0;
for time = 0:.05:3
    count = count +1;
    hl = hrr_profile (nscat, scat_range, scat_rcs, n, deltaf, prf, v, rnote,winid);
    array(count,:) = transpose(hl);
    hl(1:end) = 0;
    scat_range =  scat_range - 2 * n * v / prf;
end
figure (1)
 numb = 2*256;% this number matches that used in hrr_profile. 
 delx_meter = 15 / numb;
 xmeter = 0:delx_meter:15-delx_meter;
 imagesc(xmeter, 0:0.05:4,array)
 colormap(gray)
ylabel ('Time in seconds')

②、仿真结果

一个运动目标的合成距离像（4s 长）

三、资源自取

雷达波形相关知识点思维导图笔记

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